His death followed an order by a US judge granting a request for Mr Breyer to be sent to Germany to stand trial.

German prosecutors were hoping to put him on trial on charges of aiding in the murder of more than 200,000 Jews at Auschwitz during World War Two.

Mr Breyer, a retired toolmaker, was arrested at his home in June and placed in federal custody.

He later admitted he was a death camp guard, but said he was stationed outside and had nothing to do with the deaths.

'Coerced'

Mr Breyer emigrated to the US in 1952 and during the 1990s, the US attempted to strip him of his citizenship and deport him.

But that failed when a judge ruled he was a natural-born citizen through his mother and was coerced into joining the SS as a minor.

The new probe was led by the federal German office in charge of Nazi war crimes, which said there was new evidence, including war-era records showing he was at Auschwitz earlier than he had acknowledged.

Mr Breyer was the oldest person US officials have accused of being involved in Nazi war crimes.